Screening apparatus having rejects controlling means

ABSTRACT

Screening apparatus having a valve in the rejects conduit controlling the discharge of material therethrough. The valve includes a plurality of chambers separated by a wall containing one or more openings of smaller cross section than the chambers and is rotatably driven at a predetermined speed by a drive motor to alternately connect each chamber to the upstream portion of the rejects conduit while the other chamber is connected to the downstream portion of such conduit. The drive motor is reversible to automatically reverse the direction of rotation of the valve in the event that the latter, during rotation in either rotary direction, becomes jammed by rejected material; and a valve in the inlet conduit of the screening apparatus is automatically closed when the first-mentioned valve is not in operation.

United States Patent Vogel 1 Mar. 7, 1972 [54] SCREENING APPARATUS HAVING REJECTS CONTROLLING MEANS Primary Examiner-Tim Miles Assistant Examiner-William Cuchlinski, .l r. 1 lnvemofl Karl E 8 Attorney-Carl R. Horten, David w. Tibbott and Robert R. [73] Assignee: Improved Machinery Inc., Nashua, NH. Paqmn [22] Filed: Feb. 24, 1970 57] ABSTRACT [2i] Appl. No.: 13,558 Screening apparatus having a valve in the rejects conduit controlling the discharge of material therethrough. The valve in- [52] U S Cl 209/242 l 37/550 209/273 cludes a plurality of chambers separated by a wall containing 210/100 210/415 one or more openings of smaller cross section than the cham- 25m 251/315 bets and is rotatably driven at a predetermined speed by a [5 1] Int. Cl i 1/24 drive motor to alternately connect each chamber to the up- [58] Field 250 306 stream portion of the rejects conduit while the other chamber 209 1 7 3 1 is connected to the downstream portion of such conduit. The 3, 6 5 drive motor is reversible to automaticallyreverse the direction of rotation of the valve in the event that the latter, during rota- I I tion in either rotary direction, becomes jammed by rejected [56] Rate Cited material; and a valve in the inlet conduit of the screening ap- UNITED STATES PATENTS paratus is automatically closed when the first-mentioned valve 15 not in o eratlon. 3,363,759 1/1968 Clarke-Founder ..209/273 p 10 Claims, 5 Drawing Figures PATENTEUHAR 1:912

, INVENTOR KARL 5. V0

WMZ

ATTORNEY SCREENING APPARATUS HAVING REJECTS CONTROLLING MEANS BACKGROUND OF THE INVENTION The present invention relates to screening apparatus and more particularly to the provision of new and improved means for controlling the discharge of material through the rejects conduit of a screening apparatus.

Numerous forms and arrangements of valves or valving devices have been interposed in the rejects conduits of screening apparatus, such as for example pressurized pulp screens, for controlling the discharge of material through such conduits. It has been generally believed that valving devices employed for this purpose must provide only a relatively small flow opening as the valving devices must be restrictive to substantial flow of liquid through the rejects conduits. However, in the operation of conventional valving devices employed for this purpose, difficulties have been encountered due to the inherent tendency of the relatively small openings to become plugged with the larger solid rejected materials which then dewater to plug the rejects conduits.

SUMMARY OF THE INVENTION An object of the present invention is to provide screening apparatus with new and improved valving means for controlling the discharge of material through the rejects conduit.

Another object of the invention is to provide screening apparatus with new and improved valving means of the type set forth particularly constructed and arranged to permit discharge of the larger solid rejected material through the rejects conduit while being restrictive to the discharge of liquid therethrough.

Another object is to provide screening apparatus with new and improved valving means of the type set forth particularly constructed and arranged to substantially minimize plugging of the rejects conduit by the larger solid rejected material.

Another object is to provide screening apparatus with new and improved valving means of the type set forth which is relatively simple and economical in construction and operation.

These objects, and those other objects and advantages of the invention which will become apparent from the following description taken in connection with the accompanying drawings, are in general attained by the provision of a screening apparatus with a valve operatively associated with the rejects conduit means for controlling the discharge of. material from the screening passage to a receivertherethrough, the valve including wall means peripherally defining a plurality of chambers in the valve and the valve also including wall means separating the chambers, such separating wall means of the valve having at least one opening therethrough of lesser cross section than the chambers communicating the chambers, the chambers being relatively disposed in the valve to cause each thereof to be connected to the screening passage while the communicating chamber is connected to the receiver, the valve being rotatable to connect each chamber with the screening passage and the receiver, alternatively, and drive means connected to the valve for rotating the valve at a predetermined speed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is an elevational view, partially broken away and in section, illustrating a screening apparatus provided with one embodiment of the invention;

FIG. 2 is an enlarged elevational sectional view fragmentarily illustrating the embodiment of the invention shown in FIG. 1;

FIG. 3 is a sectional view of such embodiment taken on line 33 of FIG. 2, looking in the direction of the arrows;

FIG. 4 is a schematic view illustrating the electrical control system of the embodiment illustrated in FIGS. I3; and

FIG. 5 is an elevational sectional view generally similar to FIG. 2, but fragmentarily illustrating another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring more particularly to the drawings wherein similar reference characters designate corresponding parts throughout the several views, FIGS. 1 through 4 illustrate an embodiment of the invention applied with a screening apparatus, designated generally as 10, which is of the type disclosed in US. Pat. application Ser. No. 695 .027, filed Jan. 2, 1968 by John P. Rich and assigned to the assignee of the present invention. It will be understood, however, that this illustrated screening apparatus has been shown for the purposes of illustration only; and the invention is notlimited to application with screening apparatus of the illustrated construction but rather is applicable to other screening apparatus of other construction.

The illustrated screening apparatus 10 comprises a housing or casing having an annular sidewall 12 arranged on a horizontal axis and closed at its ends by end walls 14. An annular apertured screen or screen plate 16 is positioned within the casing concentrically with the sidewall 12 and supported at its ends by the casing end walls 14. The screen 16 is spaced from the sidewall 12 by an annular screening passage or chamber 18 which is bounded along its inner and outer peripheries by the screen outer feed face and the inner face of the sidewall 12, respectively. An inlet means communicates the screening passage 18 with a source (not shown) of the pressurized pulp suspension (or other pressurized mixture of liquid and solid material) to be screened, such inlet means being illustrated as comprising a supply conduit or pipe 20 which contains a shutoff valve 22 and is arranged to supply the pressurized pulp suspension or other mixture to the right-hand (as viewed in FIG. 1) end of the screening passage 18. Also, a rejects conduit means is connected to the screening passage 18 for discharging therefrom the portion of the pulp or other mixture rejected by. the openings in the screen 16, this rejects conduit means being shown as a vertical rejects discharge conduit 24 which at its upper end communicates with the left-hand (as viewed in FIG. 1) end of the screening passage 18. The lower end of the rejects discharge conduit 24 is illustrated as connected to discharge to a receiver 26 at atmospheric or other pressure lower than the pressure of the pulp or mixture in the screening passage 18.

A rotatable drum 28 is located within the screen I6 and rotatably supported on a hub 30 formed on the end wall 14 at 'the right-hand end of the casing. The drum 28 includes an annular sidewall 32, concentric with the sidewall 12 and the screen 16, which is spaced from the inner accepts face of the screen 16 by an annular accepts passage or chamber 34 therebetween; and such drum wall 32 carries elongated spaced vanes 36 which cooperate with therebetween pockets, during the rotation of the drum 28, to pulse the accepted portion of the pulp suspension or other mixture supplied to the accepts passage 34 through the openings in the screen 16. The drum 28 is rotatably driven by a drive motor, designated generally as 38, through the motor shaft 40, coupling 42, and thesupporting shaft 44 on which the drum 28 is mounted.

A dilution supply conduit 46, connected to a pressurized source (not shown) of suitable dilution liquid such as clean water, communicates with the left-hand end of the accepts passage 34 through a dilution supply space 48 provided between the left-hand end wall 14 and the thereadjacent end of the drum 28. The accepted portion of the pulp or mixture is discharged from the accepts passage 34 through an accepts discharge space 50, provided between the right-hand end wall 14 and the thereadjacent end of the drum 28, to an accepts discharge conduit 52 which conveys it from the apparatus 10.

During the operation of the apparatus 10, the pressurized .pulp (or other mixture of liquid and solid material to be screened) is normally continuously supplied to the screening passage 18 through the supply conduit 20; and dilution liquid is similarily normally continuously supplied to the accepts passage 34 by the dilution supply conduit 46. The drum 28 is continuously rotatably driven by the drive motor 38 to pulse the accepted portion of the pulp (or other mixture) and dilution liquid in the accepts passage 34; and such accepted portion and dilution liquid are discharged to the accepts discharge conduit 52 through the accepts discharge space 50. The portion of the pulp (or other liquid-solid mixture) which is rejected by the openings in the screen 16 is discharged from the screening passage 18 through the rejects discharge conduit 24 due to the pressure difi'erential between the mixture in the screening passage 18 and the receiver 26 connected thereto by the rejects discharge conduit 24,

In accordance with the present invention, the apparatus is provided with new and improved means for controlling the discharge of material through the rejects discharge conduit 24 to provide prompt removal of the rejected larger solid material discharged therethrough while preventing excessive liquid flow through such conduit 24. More particularly, as illustrated in FIGS. 1 through 4, a valve designated generally as 54 is interposed in the rejects discharge conduit 24 intermediate upstream and downstream portions of the latter.

The valve 54 is contained in a valve chamber 56 communicating said upstream and downstream portions of the rejects discharge conduit 24 and is mounted on bearings 58 for rotation about an axis transverse to the valve chamber 56 and the rejects discharge conduit 24. The valve 54 is connected to a drive motor 60 (illustrated as being a fractional horsepower, single-phase, reversible electric induction motor, but alternatively another suitable conventional motor such as a reversible three-phase motor) through the motor shaft 62, reduction gearing 64 and a drive shaft 66, whereby the valve 54 may be continuously rotatably driven by the drive motor 60 at a predetermined speed in alternative opposing rotary directions.

A valve chamber 70 is formed in the valve 54 at each of opposite ends thereof, the valve chambers 70 each being circum ferentially bounded by a wall 72 of the valve 54 and both being of substantially the same volume and of cross section at least that of the flow passage of the rejects discharge conduit 24. The valve 54, adjacent its center, is provided with a wall or wall means 74 which extends transversely to the chambers 70 and separates the adjacent inner portions of the latter. A single centrally disposed opening 76 is formed through the wall 72 and communicates the inner portions of the chambers 70, the opening 76 being of substantially smaller cross section than the chambers 70.

The drive motor 60 is controlled by a control means whereby, during rotation of the valve 54 in either rotary direction, the direction of valve rotation by the drive motor 60 is automatically reversed in the event a predetermined resistance to the valve rotation is encountered, such as jamming of the valve 54 by larger solid material discharged through the rejects discharge conduit 24. Also, said control means is connected to the valve 22 in the supply conduit to close such valve 22 to prevent flow of the pressurized pulp (or other mixture) through the supply conduit 20 when the valve 54 is not in operation (i.e., when the valve 54 is not being rotated by the drive motor 60).

More particularly, as illustrated in FIG. 4, the field coils 82, 84, of the drive motor 60 are connected in an electrical circuit including a ground lead 80 and an input lead 78 which contains a manually operated control switch 86 and a circuit breaker 88. The motor capacitor 90, internal starting switch 92 and two additional motor coils 93, 95 are in the conventional manner connected to the reversing contacts 94, 96, 98, 100 for the motor 60; and such contacts are provided with cooperative contacts 102, 104 connected in series with a normally closed switch 106 and a solenoid 108, The internal motor switch 92, as will be understood, is closed only during starting of the motor 60 and is open during the motor continued operation. The contacts 102, 104 are illustrated as engaging the contacts 96, 100, respectively, and (as will be hereinafter described) are actuatable between their illustrated positions and other positions wherein they engage the contacts 94, 98. respectively, by a solenoid 110 which is contacted in parallel to the contacts and in series with a normally open switch 112. A normally open switch 114, controlled by the solenoid 108 to be closed by energization of the latter and maintained closed throughout such energization, is connected in series with solenoids 116, 118 connected whereby upon energization they open the switch 106 and close the switch 112, respectively. The solenoid 118 and its controlled switch 112 are a sequence relay switch (for example, Guardian Electric Manufacturing Company Type 660 AC) with ON-OFF- ON-OFF action so that solenoid is alternately energized to alternately engage contacts 102, 104 with contacts 94, 96 and 98, 100, respectively. The solenoid 116, as will be noted, is provided with a time delay switch 119 adapted to delay energization of such solenoid 116 until a predetermined time after the switch 114 has been closed. Also, a solenoid is connected to the valve 22 to control the operation of the latter whereby the valve 22 is maintained open throughout the energization of the solenoid 120 and automatically closed upon deenergization thereof. The solenoid 120 is continuously energized with the control switch 86 and circuit breaker 88 closed, but, of course, deenergized when such switch 86 or circuit breaker 88 is open and the valve 54 is not being rotatably driven by the drive motor 60.

Throughout the before-described operation of the screening apparatus 10, the control switch 86 and circuit breaker 88 are normally maintained closed whereby the solenoid 120 is continuously energized to maintain the valve 22 open and the motor 60 is continuously powered to rotatably drive the valve 54. During operation of the motor 60 with the contacts 102, 104 in their illustrated engagement with the contacts 96, 100, respectively, the valve 54 is rotatably driven at a predetermined speed in a first rotary direction dictated by such contact engagement. During the valve rotation, the chambers 70 in the valve 54 are alternately connected to the portion of the rejects discharge conduit 24 upstream of the valve 54, each chamber 70 being so connected while the other thereof is simultaneously connected to the portion of the rejects discharge conduit 24 downstream of the valve 54. Hence, rejected solid material is received by each chamber 70 while such is connected to the upstream portion of the rejects discharge conduit 24 and discharged from the chamber 70 when the valve 54 is rotated to an inverted position wherein the chamber'70 is connected to the downstream portion of the conduit 24. During the filling of each chamber 70 with rejected solid material from the upstream portion of the conduit 24, a small amount or bubble" of air is rapidly displaced from the chamber 70 being filled through the opening 76 to the discharging chamber 70. This air bubble" rapidly blows out the solid material from the discharging chamber 70 (and hence accelerates both the filling of the chamber 70 receiving solid material and the discharging of the other chamber 70) and also allows liquid-solids flow to occur with minimal airflow upwardly through the rejects discharge conduit 24 into the screening passage 18.

The motor 60 continues to rotatably drive the valve 54 in the aforementioned first rotary direction unless and until further valve rotation in such rotary direction is prevented by jamming" of the valve 54. This valve jamming, as will be understood, could be caused by the chamber 70 being filled receiving larger rejected solid material which is sufficiently large to prevent continued valve rotation in such first rotary direction. In such event, the motor 60 stops under full power and the internal motor switch 92 closes whereby the solenoid 108 is resultantly energized and the switch 114 closed, Hence, the solenoid 118 is thereby energized to close the switch 112 andprovide resultant energization of the solenoid 110 which shifts the contacts 102, 104 to engagement with the contacts 94, 98, respectively. (It will be noted that the solenoid 116 is also energized, but only after energization of the solenoid 118 and shifting of the contacts 102, 104, to open the switch 106 whereby the solenoid 108 is thereby deenergized and the switch 114 reopened.) Hence, the motor 60 is reversed to reverse the direction of the driven rotation of the valve 54..lf the larger rejected solid material previously jamming the valve 54 does not prevent valve rotation in the reversed rotary direction, the motor 60 continues to rotatably drive the valve 54 in such reversed rotary direction and the chambers 70 fill and empty as before described. If, however, the larger solid material also prevents valve rotation in the reversed direction, the motor 60 again stops under full power and the internal motor switch 92 is reclosed. The solenoid 108 is resultantly energized to again close the switch 114 whereupon energization of the solenoid 118 recloses the switch 112 to provide energization of the solenoid 110 and resultant reshifting of the contacts 102, 104 to their illustrated engagement with the contacts 96, 100 respectively. In this manner, the motor 60 may be continuously reversed until the valve jamming ends whereupon the valve 54 continues to be rotatably driven in the direction in which the valve jamming was cleared. (In the event, however, such rotation reversal failsto end the jamming, the circuit breaker 88 automatically opens to prevent further operation of the motor 60 and cause the valve 22 to be closed.)

FIG. 5, wherein parts similar to those aforedescribed with reference to the embodiment of the invention illustrated in FIGS. 1 through 4 are designated by the reference character for their aforedescribed similar part followed by the suffix a, fragmentarily illustrates an alternative embodiment of the invention in the form of a valve 54a. The valve 54a is different from the aforedescribed valve 54 only in that the wall or wall means 740 separating the chambers 70a comprises a plurality of openings 76a of substantially smaller cross section than the flow passage of the rejects discharge conduit and is essentially a screen. The operation of the embodiment of the invention fragmentarily illustrated in FIG. 5 is the same as the aforedescribed operation of the embodiment of the invention shown in FIGS. 1 through 4.

From the aforegoing it will be seen that the invention provides new and improved means for accomplishing all of the aforementioned objects and advantages. It will be understood, however, that, although only two embodiments of the invention have been illustrated and hereinbefore specifically described, the invention is not limited merely to these two embodiments but rather contemplates other embodiments and variations constructed in accordance with its teachings.

Having thus described my invention, 1 claim:

1. In combination with a screening apparatus having a plurality of walls defining a screening passage, at least one of said walls being a screen exposed to said screening passage for screening a mixture of liquid and solid material therein, inlet means communicating with said screening passage for supplying a pressurized mixture of liquid and solid material to said screening passage, accepts outlet means operatively associated with said screen for receiving the portion of the mixture passing through said screen, a receiver at a pressure lower than the pressure in said screening passage, and rejects conduit means communicating said screening passage with said receiver for discharging the portion of the mixture rejected by said screen from said screening passage to said receiver, means for controlling the discharge of material through said rejects conduit means, said controlling means comprising a valve in said rejects conduit means intermediate said screening passage and said receiver, said valve including wall means peripherally defining a plurality of chambers in the valve and said valve also including wall means separating said chambers, said separating wall means of said valve having at least one opening therethrough of lesser cross section than said chambers communicating said chambers, said chambers being relatively disposed in said valve to cause each thereof to be connected to said screening passage while the communicating chamber is connected to said receiver, said valve being rotatable to connect each said chamber with said screening passage and said receiver, alternatively, and drive means connected to said valve for rotating said valve at a predetermined speed.

2. The combination of claim 1, wherein said valve chambers are of cross section at least that of the flow passage of said rejects conduit means.

3. In combination with a screening apparatus having a plurality of walls defining a screening passage, at least one of said walls being a screen exposed to said screening passage for screening a mixture of liquid and solid material therein, inlet means communicating with said screening passage for supplying a pressurized mixture of liquid and solid material to said screening passage, accepts outlet means operatively associated with said screen for receiving the portion of the mixture passing through said screen, a receiver at a pressure lower than the pressure in said screening passage, and rejects conduit means communicating said screening passage with said receiver for discharging the portion of the mixture rejected by said screen from said screening passage to said receiver, means for controlling the discharge of material through said rejects conduit means, said controlling means comprising a valve in said rejects conduit means intermediate upstream and downstream portions thereof, said valve having wall means peripherally defining a chamber in each of opposite ends of the valve and said valve also having wall means extending transversely to said chambers separating said chambers, said transversely extending wall means having at least one opening therethrough of lesser cross section than said chambers communicating said chambers, said valve being rotatable to connect each said chamber with the upstream portion of the rejects conduit means and simultaneously connect the other said chamber with the downstream portion of the rejects conduit means, and drive means connected to said valve for rotating said valve at a predetermined speed to alternately connect each said chamber with the upstream portion of the rejects conduit means.

4. The combination of claim 3, wherein said transversely extending wall means has a plurality of such openings therethrough.

5. The combination of claim 3, wherein said transversely extending wall means has only a single one of such openings therethrough.

6. The combination of claim 3, wherein said drive means is adapted to rotate said valve in two alternative rotary directions, and further comprising means controlling said drive means for changing the rotary direction in which it rotates said valve.

7. The combination of claim 3, wherein said drive means is adapted to rotate said valve in alternative opposing rotary directions, and further comprising control means for causing the direction of rotation of said valve by said drive means to be reversed upon predetermined resistance to rotation of said valve in either rotary direction.

8. The combination of claim 3, further comprising valve means for controlling the flow of the mixture to said screening passage through said inlet means, and means for causing said valve means to prevent such flow of the mixture when said valve is not operating.

9. The combination of claim 3, wherein said drive means is operable to rotate said valve in alternative opposing rotary directions, and further comprising valve means for controlling the flow of the mixture to said screening passage through said inlet means and control means for causing said drive means to reverse the direction of rotation in a rotary direction, said control means being connected to said valve means to cause the valve means to prevent flow of the mixture through the inlet means when said valve is not rotated by said drive means.

10. The combination of claim 3, wherein said chambers in said valve are of cross section at least that of said rejects conduit means, and said transversely extending wall means is adjacent the center of the valve. 

1. In combination with a screening apparatus having a plurality of walls defining a screening passage, at least one of said walls being a screen exposed to said screening passage for screening a mixture of liquid and solid material therein, inlet means communicating with said screening passage for supplying a pressurized mixture of liquid and solid material to said screening passage, accepts outlet means operatively associated with said screen for receiving the portion of the mixture passing through said screen, a receiver at a pressure lower than the pressure in said screening passage, and rejects conduit means communicating said screening passage with said receiver for discharging the portion of the mixture rejected by said screen from said screening passage to said receiver, means for controlling the discharge of material through said rejects conduit means, said controlling means comprising a valve in said rejects conduit means intermediate said screening passage and said receiver, said valve including wall means peripherally defining a plurality of chambers in the valve and said valve also including wall means separating said chambers, said separating wall means of said valve having at least one opening therethrough of lesser cross section than said chambers communicating said chambers, said chambers being relatively disposed in said valve to cause each thereof to be connected to said screening passage while the communicating chamber is connected to said receiver, said valve being rotatable to connect each said chamber with said screening passage and said receiver, alternatively, and drive means connected to said valve for rotating said valve at a predetermined speed.
 2. The combination of claim 1, wherein said valve chambers are of cross section at least that of the flow passage of said rejects conduit means.
 3. In combination with a screening apparatus having a plurality of walls defining a screening passage, at least one of said walls being a screen exposed to said screening passage for screening a mixture of liquid and solid material therein, inlet means communicating with said screening passage for supplying a pressurized mixture of liquid and solid material to said screening passage, accepts outlet means operatively associated with said screen for receiving the portion of the mixture passing through said screen, a receiver at a pressure lower than the pressure in said screening passage, and rejects conduit means communicating said screening passage with said receiver for discharging the portion of the mixture rejected by said screen from said screening passage to said receiver, means for controlling the discharge of material through said rejects conduit means, said controlling means comprising a valve in said rejects conduit means intermediate upstream and downstream portions thereof, said valve having wall means peripherally defining a chamber in each of opposite ends of the valve and said valve also having wall means extending transversely to said chambers separating said chambers, said transversely extending wall means having at least one opening therethrough of lesser cross section than said chambers communicating said chambers, said valve being rotatable to connect each said chamber with the upstream portion of the rejects conduit means and simultaneously connect the other said chambeR with the downstream portion of the rejects conduit means, and drive means connected to said valve for rotating said valve at a predetermined speed to alternately connect each said chamber with the upstream portion of the rejects conduit means.
 4. The combination of claim 3, wherein said transversely extending wall means has a plurality of such openings therethrough.
 5. The combination of claim 3, wherein said transversely extending wall means has only a single one of such openings therethrough.
 6. The combination of claim 3, wherein said drive means is adapted to rotate said valve in two alternative rotary directions, and further comprising means controlling said drive means for changing the rotary direction in which it rotates said valve.
 7. The combination of claim 3, wherein said drive means is adapted to rotate said valve in alternative opposing rotary directions, and further comprising control means for causing the direction of rotation of said valve by said drive means to be reversed upon predetermined resistance to rotation of said valve in either rotary direction.
 8. The combination of claim 3, further comprising valve means for controlling the flow of the mixture to said screening passage through said inlet means, and means for causing said valve means to prevent such flow of the mixture when said valve is not operating.
 9. The combination of claim 3, wherein said drive means is operable to rotate said valve in alternative opposing rotary directions, and further comprising valve means for controlling the flow of the mixture to said screening passage through said inlet means and control means for causing said drive means to reverse the direction of rotation in a rotary direction, said control means being connected to said valve means to cause the valve means to prevent flow of the mixture through the inlet means when said valve is not rotated by said drive means.
 10. The combination of claim 3, wherein said chambers in said valve are of cross section at least that of said rejects conduit means, and said transversely extending wall means is adjacent the center of the valve. 